1. Field of the Invention
This invention relates to an acceleration control apparatus for a vehicle, and more particularly to an acceleration control apparatus for a vehicle suitable to prevent an excessive sudden acceleration operation of the vehicle to improve the smoothness of the operation of the vehicle.
2. Description of Background Art
A motorcycle is known wherein sudden acceleration upon the starting of the operation of the vehicle is limited to achieve smooth acceleration. For example, in an acceleration control apparatus for a motorcycle disclosed in Japanese Patent Laid-Open No. Hei 7-180644, taking notice of the fact that, upon acceleration, the posture of a vehicle varies and a bifurcated member (front fork) for supporting the front wheel is extended, sudden acceleration is detected based on the degree of the extension of the front fork to retard the ignition timing.
The acceleration control apparatus described above has the following problems. First, since a space in which a sensor for detecting the extension amount of the front fork is to be provided is assured, the degree of freedom in the designing of a member around the fork to which the sensor is attached is deteriorated. Second, since the posture of the vehicle changes and a change occurs with the front fork only after sudden acceleration has occurred actually, the conventional acceleration control apparatus cannot achieve an object of, for example, preventing sudden acceleration to make a connection of a centrifugal clutch smooth, particularly to provide a smooth the state of the centrifugal clutch when connection begins. Third, since the degree of the extension of the front fork varies depending upon the number of passengers or the weight of a passenger or passengers even if the acceleration is the same, it is difficult to precisely set a reference value for the extension amount of the front fork to be used for discrimination of a sudden acceleration.
It is an object of the present invention, taking the subjects described above into consideration, to provide an acceleration control apparatus for a vehicle which prevents sudden acceleration of the vehicle to achieve a suitable acceleration state which provides a good comfortable ride of the vehicle.
In order to attain the object described above, according to the present invention, an accelerator controlling apparatus for a vehicle has a first characteristic in that it comprises supervision means for starting the supervision of a sudden acceleration when predetermined conditions corresponding to the start up of the vehicle are satisfied with regard to at least two selected from among a vehicle speed, a throttle opening and an engine speed, centrifugal clutch for interrupting driving force transmission between an engine and a driving wheel in response to the engine speed. An acceleration control means is provided for limiting the engine output power when the throttle opening during a period of the supervision by the supervision means reaches a predetermined value corresponding to sudden acceleration. According to the present invention, the engine speed which is one of the predetermined conditions for the startup, is set to a low speed region lower than a value at which the centrifugal clutch is connected.
Further, an acceleration control apparatus for a vehicle has a second characteristic in that the acceleration control means is ignition retard means which sets an ignition timing of a small angle of lead and maintains the ignition timing for a predetermined period of time, and has a third characteristic in that it comprises an ignition timing returning means for returning the ignition timing of the small angle of lead set by the ignition retard means stepwise to a normal ignition timing after lapse of the predetermined period of time.
Furthermore, according to the present invention, an acceleration control apparatus for a vehicle has a fourth characteristic in that the vehicle is a saddle type vehicle. In addition, the present invention is directed to a centrifugal clutch which is a dry centrifugal clutch.
According to the first to fourth characteristics, the presence or absence of a sudden acceleration is supervised based on the throttle opening for the predetermined period of time after it is determined that the predetermined conditions are satisfied and the vehicle is in a startup state. If a sudden opening of the throttle corresponding to sudden acceleration is detected, then the engine output power is limited.
The output power of the engine can be limited particularly before the connection of the centrifugal clutch and the feeling in the beginning of the connection of the centrifugal clutch can be improved. In addition, even if the control amount is increased, sudden acceleration can be limited without making the operation of the vehicle unstable because this does not have an influence on the feeling because the clutch is not yet connected. Further, the present invention is suitable for a saddle type vehicle for which the smoothness upon the startup is particularly required because the vehicle is light in weight.
According to another feature of the present invention, since not only a miniaturization of the clutch is possible but also a sudden acceleration from a half-clutch state which appears notably where a dry type centrifugal clutch is adopted can be moderated. Thus, a miniaturization of the clutch and prevention of a sudden acceleration can be achieved simultaneously.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.